@sixsixtwo
Not that you are doing any wrong, but knowing that the extender works in half-duplex meaning it takes the data from the device then sends it to the router. When connecting directly to the router, the router works in full-duplex meaning data is received and sent at the same time.
A common misconception is that an extender equals a boost in speed which is not always the case. If your device had slow speed as a result of a very weak signal then using an extender to boost the signal should also increase the speeds.
In your case, you are better off without the extender at least for the device in question, but maybe useful if you have something further away.